buckets.swift

// Protocol
protocol Feed {
    var url : String { get }
}

// Concrete classes
class LocalFeed : Feed {
    var url : String = "file://Local"
}

class RemoteFeed : Feed {
    var url : String = "http://Remote"
}

// Hash/equality policy - don't pollute protocols or classes with this nonsense
// We do things this way because we're going to use Set and Set is an intrusive container - requires the contained objects to have special members
class Containable : Hashable {
    var element: Feed
    var hashValue: Int { return element.url.hashValue }
    init(_ element : Feed) {
        self.element = element
    }
}

func ==(lhs: Containable, rhs: Containable) -> Bool {
    return lhs.element.url == rhs.element.url
}
// Container
typealias Container = Set<Containable>

// Made Bucket a SequenceType so we can loop over it directly
class Bucket : SequenceType {
    //typealias Generator = LazyMapGenerator<Container.Generator, Feed>
    typealias Generator = AnyGenerator<Feed>
    
    var _feeds : Container = Container()
    
    func add(feed : Feed) {
        _feeds.insert(Containable(feed))
    }
    
    var feeds : [Feed] {
    	return _feeds.map { $0.element };
    }

    func generate()->Generator {
        return AnyGenerator(_feeds.lazy.map { $0.element }.generate());
    }
}


// Use the code
var bucket = Bucket();
bucket.add(LocalFeed())
bucket.add(RemoteFeed())

for feed in bucket {
    print(feed.url)
}